It is proposed conventionally to attach an image projection device on a wrist of a manipulator for projection light onto an object, on which the manipulator will operate next (JP 2004-122313A). A user is thus enabled to realize the object, on which the manipulator will operate next, by the projected light.
In some instances, the user does not recognize the projected light, that is, the user is not aware of the projected light at all. When the user is not aware of the projected light, the user will recognize movement of manipulator only after the manipulator has moved very closely to a body of the user.